Spread-spectrum changeable base station

ABSTRACT

A conference calling spread-spectrum communications system and method using a plurality of spread-spectrum units, any one of which may serve as the base station and where the base station may be changed from one spread-spectrum unit to another upon command. Each spread-spectrum unit includes a base subunit, a remote subunit, and a command subunit. An operator may initiate from the command subunit of a particular spread-spectrum unit, a command signal to activate the base subunit of the particular spread-spectrum unit. Upon initiating the command signal, the particular spread-spectrum unit is activated as the base station and the command signal is broadcast to the remaining plurality of spread-spectrum units. At a respective remote subunit of each of the remaining plurality of spread-spectrum units, the command signal is received and, in response to receiving the command signal, the respective remote subunit in each of the remaining plurality of spread-spectrum units is activated to operate the remaining plurality of spread-spectrums units as remote units.

BACKGROUND OF THE INVENTION

This invention relates to spread-spectrum communications, and moreparticularly, to a method and system for handing off a base stationamong a plurality of users in a spread-spectrum network.

DESCRIPTION OF THE RELEVANT ART

Spread-spectrum modulation is a well developed art, in terms ofgenerating chipping sequences, and spread-spectrum processing datasignals with the chipping sequences. Using this technology,communication links may be established among a transmitter and areceiver in remote locations. Also, networks may be established, using aconference calling spread-spectrum technique. Conference callingspread-spectrum techniques are disclosed in U.S. Pat. No. 5,179,572entitled SPREAD SPECTRUM CONFERENCE CALLING SYSTEM AND METHOD, toSchilling, and in U.S. Pat. No. 5,263,045, entitled SPREAD SPECTRUMCONFERENCE CALL SYSTEM AND METHOD, to Schilling.

A problem may exist where a spread-spectrum conference calling system isset up, but the base station may need to change hands. For example, in amilitary environment, a platoon may use spread-spectrum modulation forconference calling among the members of the platoon. A particular unitin the platoon may be designated as the base station. The cited priorart does not teach how to change a base station from one platoon toanother or what would happen among units in the platoon in the event itbecame necessary to effectuate such a change.

SUMMARY OF THE INVENTION

A general object of the invention is a conference callingspread-spectrum communications system and method, where the base stationmay be changed upon demand.

Another object of the invention is a spread-spectrum conference callingtechnique where any unit may serve as a base station.

According to the present invention, as embodied and broadly describedherein, a spread-spectrum system having a plurality of spread-spectrumunits is provided. Each spread-spectrum unit is capable of operating asa base station and as a remote station. Each spread-spectrum unitincludes a base subunit, a remote subunit, and a command subunit.

The method of the present invention includes receiving in the basesubunit at a first frequency a plurality of spread-spectrum signalstransmitted from the plurality of spread-spectrum units. The pluralityof spread-spectrum signals are despread and demodulated in the basesubunit to generate a plurality of demodulated signals. The plurality ofdemodulated signals are combined, and a local signal, such as datasignal or a voice signal from the user of the unit, is also combined togenerate a combined signal. The base subunit converts the combinedsignal to a base-data signal. The base subunit spread-spectrum processesthe base-data signal, and transmits using radio waves thespread-spectrum-processed-base-data signal at a second frequency as abase-spread-spectrum signal.

At each of the spread-spectrum units, in the respective remote subunit,at the second frequency, the base-spread-spectrum signal is received.The remote subunit includes circuitry for despreading thebase-spread-spectrum signal, and demodulating thedespread-base-spread-spectrum signal as a base-analog signal. The remotesubunit also may take the local voice signal, designated herein as aremote-analog signal, and convert the remote-analog signal to aremote-data signal. The remote subunit spread-spectrum processes theremote-data signal and transmits the remote-data signal at the firstfrequency as one of the plurality of spread-spectrum signals.

An operator may initiate from the command subunit, a command signal toactivate the base subunit. Accordingly, upon initiating the commandsignal, the command signal is broadcast to the plurality ofspread-spectrum units. At each of the spread-spectrum units, in therespective remote subunit, the command signal is received, and inresponse to receiving the command signal, the remote subunit isactivated.

Additional objects and advantages of the invention are set forth in partin the description which follows, and in part are obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention also may be realized and attained bymeans of the instrumentalities and combinations particularly pointed outin the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate preferred embodiments of theinvention, and together with the description serve to explain theprinciples of the invention.

FIG. 1A is a block diagram of a base subunit using a plurality ofmixers;

FIG. 1B is a block diagram of a base subunit using a plurality ofmatched filters;

FIG. 2A is a block diagram of a remote subunit using a mixer;

FIG. 2B is a block diagram of a remote subunit using a matched filter;and

FIG. 3 is a block diagram of a command subunit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference now is made in detail to the present preferred embodiments ofthe invention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals indicate like elementsthroughout the several views.

The present invention provides a unique solution to the problem of aplurality of spread spectrum units in use in a mobile environment inwhich any one of the spread-spectrum units is vulnerable toneutralization while maintaining communication between all thespread-spectrum units remains crucial. The spread-spectrum changeablebase station finds application in a platoon of units, in an armyenvironment, or in a law enforcement application, where a transportablebase station might be set up for controlling a plurality of spreadspectrum remote units. The problem being addressed for each of theseapplications is what happens when the base unit becomes disabled ornonfunctional. In the military environment, the base station may bedestroyed. In a law enforcement situation, the mobility of the pluralityof spread-spectrum units may have a requirement that the base stationchange from one unit to another.

The spread-spectrum system has a plurality of spread-spectrum units,with each spread-spectrum unit having a base subunit, a remote subunit,and a command subunit. The use of the term "subunits" for designatingthe base subunit, remote subunit, and command subunit, is for purposesof illustrating the invention. The invention may be built as one totallyintegrated unit, or as a mixture of more than one unit.

The base subunit is illustratively shown in FIGS. 1A and 1B. The basesubunit includes receiving means, despreading means, demodulating means,combining means, converting means, spread-spectrum processing means, andtransmitting means. The despreading means is coupled between thereceiving means and the demodulating means. The combining means iscoupled to the demodulating means and the converting means. Thespread-spectrum processing means is coupled to the converting means andthe transmitting means.

The receiving means is shown in FIG. 1A as antenna 11 coupled to radiofrequency/intermediate frequency (RF/IF) amplifier and filter section12. The despreading means is illustrated as a plurality of mixers 13,14, 15. As shown in FIG. 1B, the despreading means may also be embodiedas a plurality of matched filters 22, 23, 24. Each of the plurality ofmixers 13, 14, 15 has a chipping-sequence g₁ (t), g₂ (t), . . . , g_(N)(t), respectively, for mixing with the received spread-spectrum signal.The plurality of chipping sequences is matched to the chipping sequenceof the desired spread-spectrum signal to be despread.

The demodulating means and combining means is shown as the demodulator16 and combiners 17A, 17B. Combiners 17A, 17B may be a single combinerperforming the combining function, or separate combiners. The convertingmeans is shown as an analog-to-digital converter 18. The spread-spectrumprocessing means is illustrated as product device 19, having a chippingsequence for spreading the data signal from analog-to-digital converter18. The transmitting means is illustrated as transmitter 20 and antenna21.

The RF/IF amplifier and filter circuits 12 are coupled to the antenna 11and to the plurality of mixers 13, 14, 15. The plurality of mixers 13,14, 15 is coupled to the demodulator 16 and combiner 17A, 17B. Theanalog-to-digital converter 18 is coupled to the combiner 17B and to theproduct device 19. The transmitter 20 is coupled to the product device19 and to antenna 21. Antenna 21 and antenna 11 may be the same antennawith the appropriate isolation circuits, or different antennas.

The RF/IF amplifier and filter circuits 12 receive at a first frequency,f₁, a plurality of spread-spectrum signals transmitted from theplurality of spread-spectrum units. The plurality of spread-spectrumsignals are despread by the plurality of mixers 13, 14, 15. As shown inFIG. 1B, the despreading means may also be embodied as a plurality ofmatched filters 22, 23, 24. The output of the plurality of mixers 13,14, 15 is a plurality of despread-spread-spectrum signals. Thedemodulator 16 demodulates the plurality of despread-spread-spectrumsignals to generate a plurality of demodulated signals. The combiner 17Acombines the plurality of demodulated signals. The combined plurality ofdemodulated signals and a local signal from the base station may becombined by second combiner 17B to generate a combined signal. The term"combined signal", as used herein, is an analog signal including thevoice of the base station and the combined demodulated signals of thecombiners 17A, 17B.

The combined signal is converted to a base-data signal byanalog-to-digital converter 18. The term "base-data signal," as usedherein, is the digital signal coming from the analog-to-digitalconverter 18, and includes the converted analog signals and the datasignal at the base station.

The product device 19 spread-spectrum processes the base-data signalfrom analog-to-digital converter 18, with a base-chipping sequence. Thespread-spectrum-processed-base-data signal is transmitted as abase-spread-spectrum signal by transmitter 20 at the second frequencyf₂. Antenna 11 and antenna 21 may be a single antenna, serving both thereceiver and transmitter.

The remote subunit is illustrated in FIGS. 2A and 2B and includes areceiver portion, a transmitter portion, receiving means, despreadingmeans, and demodulating means. The transmitting portion includesconverting means, spread-spectrum processing means and transmittingmeans. The receiving means receives at the second frequency thebase-spread-spectrum signal. The despreading means despreads thebase-spread-spectrum signal as a despread-base-spread-spectrum signal.The demodulating means demodulates the despread-base-spread-spectrumsignal as a base-analog signal.

The converting means converts a remote-analog signal to a remote-datasignal. The remote-analog signal typically is the voice of the remotestation. The base-analog signal typically is the plurality of voicesignals from the base station. The spread-spectrum processing meansprocesses the remote-data signal with a remote-chipping sequence. Thetransmitting means transmits at the first frequency thespread-spectrum-processed-remote-data signal as one of the plurality ofspread-spectrum signals, which are received at the base subunit.

As shown in FIG. 2A, the receiving means includes an antenna 31 andRF/IF amplifier and filter circuitry 32. The despreading means anddemodulating means are embodied as mixer 33 and demodulator 34,respectively. As shown in FIG. 2B, the despreading means may also beembodied as a matched filter 39. The RF/IF amplifier and circuitry 32 iscoupled between antenna 31 and the mixer 33. The demodulator 34 iscoupled to the mixer 33.

The base-spread-spectrum signal at antenna 31 is amplified and filteredby RF/IF. The base-spread-spectrum signal is despread by thebase-chipping sequence by mixer 33 to generate thedespread-base-spread-spectrum signal. The demodulator 34 demodulates thedespread-base-spread-spectrum signal as a base-analog signal. The outputof the demodulator 34 is the plurality of voice signals from the basestation.

The transmitter section of the remote subunit may have the convertingmeans embodied as analog-to-digital converter 35, the spread-spectrumprocessing means embodied as product device 36 and the transmittingmeans embodied as transmitter 37 coupled to antenna 38. The productdevice 36 is coupled between the analog-to-digital converter 35 and thetransmitter 37.

The analog-to-digital converter 35 converts the voice of the remotesignal, designated here as the remote-analog signal, to a remote-datasignal. The remote-data signal is spread-spectrum processed by theproduct device 36 using remote-chipping sequence. The output of theproduct device 36 is the spread-spectrum-processed-remote-data signal.The transmitter 37 transmits the spread-spectrum-processed-remote-datasignal using antenna 38, as one of the plurality of spread-spectrumsignals. Antenna 31 and antenna 38 may be combined as a single antennaserving both functions.

The command subunit is illustrated in FIG. 3. The command subunitincludes initiating means, broadcasting means, and receiving means. Theinitiating means initiates a command signal, upon activation by thelocal user of that spread-spectrum unit. The command signal activatesthe base subunit in that spread-spectrum unit. The broadcasting meansbroadcasts the command signal to the plurality of spread-spectrum units.The receiving means receives the command signal when broadcast from adifferent spread-spectrum unit. The activating means activates theremote subunit upon receiving the command signal.

The initiating means is illustrated in FIG. 3 as a push button switch43. The broadcasting means is illustrated as a transmitter portion ofthe transmitter/receiver 42. The transmitter transmits at frequency f₃.The receiving means is illustrated as the receiver portion oftransmitter/receiver 42. The receiver receives at frequency f₃. Thetransmitter/receiver 42 is coupled to antenna 41 for radiating andreceiving signals. The activating means includes the necessary circuitryfor disconnecting the base subunit and activating the remote subunit ofa particular spread-spectrum unit. The activating means is illustratedas control circuitry 44. The present invention may also be used for datain place of voice signals.

In use, a particular spread-spectrum unit might be operating with itsremote subunit activated. Thus, the remote subunit of that particularspread-spectrum unit receives at the second frequency thebase-spread-spectrum signal, and despreads the base-spread-spectrumsignal as a despread-base-spread-spectrum signal. Thedespread-base-spread-spectrum signal is demodulated. Thus, thatparticular spread-spectrum unit receives all of the base signals via itsremote subunit. While transmitting to the plurality of spread-spectrumunits, that particular spread-spectrum unit converts the voice signal,embodied as the remote-analog signal, to the remote-data signal. Theremote-data signal is spread-spectrum processed and transmitted at thefirst frequency as one of the plurality of spread-spectrum signals.

Upon initiation of the command signal by the user of that particularspread-spectrum unit, by pushing push button 43, that particularspread-spectrum unit switches from operating with the remote subunit tooperating with the base subunit. At the same time, the command signal isradiated to the other spread-spectrum units of the plurality ofspread-spectrum units. Upon receiving the command signal, each of thespread-spectrum units has its remote subunit activated and thereafterworks in a remote subunit mode. The particular spread-spectrum unit hasthen become the base station.

When operating as the base station, the particular spread-spectrum unithas its base subunit activated. Accordingly, the plurality ofspread-spectrum signals transmitted from the plurality ofspread-spectrum units at each unit, is received by the RF/IF amplifierand circuitry 12 via antenna 11. The plurality of spread-spectrumsignals are despread by the plurality of mixers 13, 14, 15, anddemodulated by the demodulator 16 which outputs a demodulated signal.The plurality of demodulated signals from combiner 17A are the voicesfrom the plurality of remote stations. The voices from the plurality ofremote stations are combined with the voice of the base station bycombiner 17B, and converted by analog-to-digital converter 18 to thebase-data signal. The base-data signal is spread-spectrum processed bythe product device 19 and transmitted by transmitter 20 and via antenna21 at the second frequency.

It will be apparent to those skilled in the art that variousmodifications can be made to the spread-spectrum changeable base stationof the instant invention without departing from the scope or spirit ofthe invention, and it is intended that the present invention covermodifications and variations of the spread-spectrum changeable basestation provided they come within the scope of the appended claims andtheir equivalents.

I claim:
 1. A spread-spectrum system having a plurality ofspread-spectrum units, with each spread-spectrum unit of said pluralityof spread-spectrum units capable of operating as a base station and as aremote station, each spread-spectrum unit of said plurality ofspread-spectrum units comprising:a base subunit including,means forreceiving at a first frequency a plurality of spread-spectrum signalstransmitted from the plurality of spread-spectrum units, respectively;means for despreading the plurality of spread-spectrum signals as aplurality of despread-spread-spectrum signals, respectively; means fordemodulating the plurality of despread-spread-spectrum signals, togenerate a plurality of demodulated signals, respectively; means forcombining the plurality of demodulated signals, and a local signal, as acombined signal; means for converting the combined signal to a base-datasignal; means for spread-spectrum processing the base-data signal; meansfor transmitting at a second frequency thespread-spectrum-processed-base-data signal as a base-spread-spectrumsignal; and a remote subunit, including,means for receiving at thesecond frequency the base-spread-spectrum signal; means for despreadingthe base-spread-spectrum signal as a despread-base-spread-spectrumsignal; means for demodulating the despread-base-spread-spectrum signalas a base-analog signal; means for converting a remote-analog signal toa remote-data signal; means for spread-spectrum processing theremote-data signal; and means for transmitting at the first frequencythe spread-spectrum-processed-remote-data signal as one of the pluralityof spread-spectrum signals.
 2. The spread-spectrum system as set forthin claim 1, wherein said despreading means within said base subunitincludes:a plurality of product devices coupled to said generating meansfor despreading the plurality of spread-spectrum signals as theplurality of despread-spread-spectrum signals.
 3. The spread-spectrumsystem as set forth in claim 1, wherein said despreading means withinsaid base subunit includes a plurality of matched filters, with each ofsaid plurality of matched filters having an impulse response matched toa plurality of chipping sequences, with the plurality of spread-spectrumsignals having a plurality of data signals spread-spectrum processedwith the plurality of chipping sequences, respectively.
 4. Thespread-spectrum system as set forth in claim 1, wherein saidspread-spectrum processing means within the base subunit includes aproduct device.
 5. The spread-spectrum system as set forth in claim 1,wherein said despreading means within the remote subunit includes amixer for despreading the base-spread-spectrum signal as thedespread-base-spread-spectrum signal.
 6. The spread-spectrum system asset forth in claim 1, wherein said despreading means within the remotesubunit includes a matched filter for despreading thebase-spread-spectrum signal as the despread-base-spread-spectrum signal.7. A method of using a spread-spectrum system having a plurality ofspread-spectrum units, with each spread-spectrum unit of said pluralityof spread-spectrum units capable of operating as a base station and as aremote station, each spread-spectrum unit of said plurality ofspread-spectrum units having a base subunit, a remote subunit, and acommand subunit, the method comprising the steps of:receiving in a basesubunit of a first spread-spectrum unit at a first frequency a pluralityof spread-spectrum signals transmitted from the plurality ofspread-spectrum units, respectively; despreading in the base subunit ofthe first spread-spectrum unit the plurality of spread-spectrum signals;demodulating in the base subunit the plurality ofdespread-spread-spectrum signals, to generate a plurality of demodulatedsignals, respectively; combining in the base subunit of the firstspread-spectrum unit the plurality of demodulated signals, and a localsignal, as a combined signal; converting in the base subunit of thefirst spread-spectrum unit the combined signal to a base-data signal;spread-spectrum processing in the base subunit of the firstspread-spectrum unit the base-data signal; transmitting from the basesubunit of the first spread-spectrum unit at a second frequency thespread-spectrum-processed-base-data signal as a base-spread-spectrumsignal; receiving in a remote subunit of a second spread-spectrum unitat the second frequency the base-spread-spectrum signal; despreading inthe remote subunit of the second spread-spectrum unit thebase-spread-spectrum signal; demodulating in the remote subunit of thesecond spread-spectrum unit the despread-base-spread-spectrum signal asa base-analog signal; converting in the remote subunit of the secondspread-spectrum unit a remote-analog signal to a remote-data signal;spread-spectrum processing in the remote subunit of the secondspread-spectrum unit the remote-data signal; and transmitting from theremote subunit of the second spread-spectrum unit at the first frequencythe spread-spectrum-processed-remote-data signal as one of the pluralityof spread-spectrum signals.